The increasing prevalence of mental illness in children requires that pediatricians improve detection of behavioral health (BH) problems to identify previously unidentified children and facilitate entry into mental health treatment. Yet, little is known about the impact of pediatric BH screening on health care utilization and psychotropic medication use. Expanding this knowledge is critical to informing the development of screening programs and assessing their cost effectiveness. Towards this end, the study will explore the relationship between implementation of pediatric BH screening and the quantity and quality of BH and non-BH care use. The specific aims of the study are:1) To evaluate the impact of BH screening at the well-child visit (6.5 to 16.5 year olds) on the quantity and quality of health care use (primary care, ambulatory, in-patient and emergency department BH and non-BH visits) and psychotropic medication use in the Cambridge Health Alliance (CHA) system and state-wide among Medicaid children and adolescents; and 2) To determine the magnitude of racial/ethnic, age and socio-economic (SES) differences regarding the impact of BH screening on the quantity and quality of health care use (primary care, ambulatory, in-patient and emergency department BH and non-BH visits) and psychotropic medication in the same systems. To achieve these aims, we propose an innovative, exploratory, population-based, longitudinal study using an interrupted time series (ITS) design to examine changes in population utilization rates of BH and non-BH health care after the implementation of BH screening in two environments: CHA-a local safety-net system-and statewide among Medicaid insured children. We will analyze existing data from 4 clinics of CHA prior to and following initiation of BH screening with the Pediatric Symptom Checklist (PSC) at well child visits. CHA initiated screening in 2003 - 4 years prior to statewide mandatory screening. Then to validate these findings, we will use Medicaid administrative claims data for Massachusetts, prior to and following the Rosie D vs. Romney lawsuit remedy in 2008, which mandated statewide BH screening at pediatric preventive visits, and the control state of New York where no mandatory screening is required. The combination of analyses will provide a set of results spanning multiple populations and payers thus offering an innovative approach to minimizing inherent biases and maximizing strengths and generalizability. Recognizing that thresholds for dysfunction, symptom disclosure, and interpretation of screening items, may vary across ethnicities and other groups, we will examine the relationship between BH screening and utilization by ethnicity/race, SES and age. We will use the same datasets and perform stratified ITS analyses. Overall, the study's significance lies in its implications for child mental health policy and primary care practices. This investigation will generate results that have the potential to inform child behavioral health screening practices nationally while providing important data for future child mental health interventions.